Pressure Collapse of the Magnetic Ordering in MnSi via Thermal Expansion

The itinerant quasi-ferromagnetic metal MnSi has been studied by detailed thermal expansion measurements under pressures and magnetic fields. A sudden decrease of the volume at the critical pressure Pc ~1.6 GPa has been observed and is in good agreement with the pressure variation of the volume fraction of the spiral magnetic ordering. This confirms that the magnetic order disappears by a first order phase transition. The energy change estimated by the volume discontinuity on crossing Pc is of similar order as the Zeeman energy of the transition from the spiral ground state to a polarized paramagnetic one under magnetic field. In contrast to the strong pressure dependence of the transition temperature, the characteristic fields are weakly pressure dependent, indicating that the strength of the ferromagnetic and the Dzyaloshinskii-Moriya interactions do not change drastically around Pc. The evaluated results of the thermal expansion coefficient and the magnetostriction are analyzed thermodynamically. The Sommerfeld coefficient of the linear temperature term of the specific heat is enhanced just below Pc. The magnetic field-temperature phase diagrams in the ordered and paramagnetic phases are also compared. Comparison is made with other heavy fermion compounds with first order phase transition at 0 K.Comment: 9 pages, 13 figures, accepted to be published in JPS

Identification and Validation of Novel Cerebrospinal Fluid Biomarkers for Staging Early Alzheimer's Disease

Ideally, disease modifying therapies for Alzheimer disease (AD) will be applied during the 'preclinical' stage (pathology present with cognition intact) before severe neuronal damage occurs, or upon recognizing very mild cognitive impairment. Developing and judiciously administering such therapies will require biomarker panels to identify early AD pathology, classify disease stage, monitor pathological progression, and predict cognitive decline. To discover such biomarkers, we measured AD-associated changes in the cerebrospinal fluid (CSF) proteome.CSF samples from individuals with mild AD (Clinical Dementia Rating [CDR] 1) (n = 24) and cognitively normal controls (CDR 0) (n = 24) were subjected to two-dimensional difference-in-gel electrophoresis. Within 119 differentially-abundant gel features, mass spectrometry (LC-MS/MS) identified 47 proteins. For validation, eleven proteins were re-evaluated by enzyme-linked immunosorbent assays (ELISA). Six of these assays (NrCAM, YKL-40, chromogranin A, carnosinase I, transthyretin, cystatin C) distinguished CDR 1 and CDR 0 groups and were subsequently applied (with tau, p-tau181 and Aβ42 ELISAs) to a larger independent cohort (n = 292) that included individuals with very mild dementia (CDR 0.5). Receiver-operating characteristic curve analyses using stepwise logistic regression yielded optimal biomarker combinations to distinguish CDR 0 from CDR>0 (tau, YKL-40, NrCAM) and CDR 1 from CDR<1 (tau, chromogranin A, carnosinase I) with areas under the curve of 0.90 (0.85-0.94 95% confidence interval [CI]) and 0.88 (0.81-0.94 CI), respectively.Four novel CSF biomarkers for AD (NrCAM, YKL-40, chromogranin A, carnosinase I) can improve the diagnostic accuracy of Aβ42 and tau. Together, these six markers describe six clinicopathological stages from cognitive normalcy to mild dementia, including stages defined by increased risk of cognitive decline. Such a panel might improve clinical trial efficiency by guiding subject enrollment and monitoring disease progression. Further studies will be required to validate this panel and evaluate its potential for distinguishing AD from other dementing conditions

Adaptation of the Bridgman anvil cell to liquid pressure mediums

The advantage of Bridgman anvil pressurecells is their wide pressure range and the large number of wires which can be introduced into the pressure chamber. In these pressurecells, soft solidpressure mediums such as steatite are used. We have succeeded in adapting the Bridgman cell to liquidpressure mediums. With this breakthrough, it is now possible to measure in very good hydrostaticpressure conditions up to 7GPa, which is about twice the pressure attainable in piston-cylinder cells. The pressure gradient in the cell, estimated from the superconducting transition width of lead, is reduced by a factor of 5 in the liquid medium with respect to steatite. By using nonmagnetic materials for the anvils and the clamp and due to the small dimensions of the latter, our device is specially suitable for magnetotransport measurements in dilution fridges. This pressurecell has been developed to measure very fragile and brittle samples such as organic conductors.Resistivity measurements of (TMTTF)2BF4 performed in a solid and a liquidpressure medium demonstrate the necessity of hydrostaticpressure conditions for the study of organic conductors at high pressures

Competition for food in swans: an experimental test of the truncated phenotype distribution

1. Ideal free models for unequal competitors predict a truncated competitor phenotype distribution among patches when relative payoffs of phenotypes vary across patches. Partial truncation is expected under field conditions. This prediction was tested in a field experiment with an overwintering population of mute swans (Cygnus olor). 2. Two food patches were generated in which adult and subadult swans were expected to have different relative success. In one patch ('clumped'), pieces of bread were thrown over a small area on the water surface. In the other patch, pieces of bread were scattered over a larger area. 3. When only one patch was offered at a time (no choice situation), adult swans were more successful than subadult swans in the 'clumped' patch, but were similarly successful in the 'scattered' patch. Relative payoffs of adult and subadult swans differed significantly between patches. 4. When the two patches were offered simultaneously, black-headed gulls (Larns ridibundus) competed with the swans to a considerable extent in some replicates. The gulls appeared to be the poorest competitors. They snatched more bread in the scattered than in the clumped patch. Both classes of swans avoided the scattered patch but not the clumped patch with increasing competition from gulls. Gulls preferred the scattered patch and swans increasingly preferred the clumped patch under gull competition, creating a partially truncated distribution. 5. Without the four replicates in which the gulls had consumed more than 25% of the bread, the percentage of adult swans that chose the clumped patch was significantly higher than the percentage of subadult swans that chose that patch. This is the first experimental verification of a partially truncated phenotype distribution. Subadult swans significantly preferred the scattered patch whereas adults tended to prefer the clumped patch. This distribution was predicted from the 'no choice' experiment, where competition by gulls had been similarly weak

Cartilage oligomeric matrix protein neoepitope in the synovial fluid of horses with acute lameness : A new biomarker for the early stages of osteoarthritis

Background: Clinical tools to diagnose the early changes of osteoarthritis (OA) that occur in the articular cartilage are lacking. Objectives: We sought to identify and quantify a novel cartilage oligomeric matrix protein (COMP) neoepitope in the synovial fluid from the joints of healthy horses and those with different stages of OA. Study design: In vitro quantitative proteomics and assay development with application in synovial fluids samples obtained from biobanks of well-characterised horses. Methods: Articular cartilage explants were incubated with or without interleukin-1β for 25 days. Media were analysed via quantitative proteomics. Synovial fluid was obtained from either normal joints (n = 15) or joints causing lameness (n = 17) or with structural OA lesions (n = 7) and analysed for concentrations of the COMP neoepitope using a custom-developed inhibition enzyme-linked immunosorbent assay (ELISA). Explants were immunostained with polyclonal antibodies against COMP and the COMP neoepitopes. Results: Semitryptic COMP peptides were identified and quantified in cell culture media from cartilage explants. A rabbit polyclonal antibody was raised against the neoepitope of the N-terminal portion of one COMP fragment (sequence SGPTHEGVC). An inhibition ELISA was developed to quantify the COMP neoepitope in synovial fluid. The mean concentration of the COMP neoepitope significantly increased in the synovial fluid from the joints responsible for acute lameness compared with normal joints and the joints of chronically lame horses and in joints with chronic structural OA. Immunolabelling for the COMP neoepitope revealed a pericellular staining in the interleukin-1β-stimulated explants. Main limitations: The ELISA is based on polyclonal antisera rather than a monoclonal antibody. Conclusions: The increase in the COMP neoepitope in the synovial fluid from horses with acute lameness suggests that this neoepitope has the potential to be a unique candidate biomarker for the early molecular changes in articular cartilage associated with OA